AMES, Iowa (AP) - David Johnson ran for a career-high 199 yards and two touchdowns and caught passes for two more scores to lead Northern Iowa past Iowa State 28-20 on Saturday night.

Northern Iowa, seeking a return to the FCS playoffs after a rare losing record in 2012, jumped to a 21-7 lead on a steamy Midwest evening and handed Iowa State its first season-opening loss in five seasons under coach Paul Rhoads. It was just the fifth victory for the Panthers in 28 games with the Cyclones, who are coming off two straight bowl appearances.

Iowa State drew to 21-20 on Cole Netten's third-quarter field goals of 23 and 38 yards, the first of his career. But Johnson caught a short pass from Kollmorgen, slipped through three defenders and went 29 yards for a touchdown early in the fourth quarter for an eight-point lead that held up.

Johnson, a 6-foot-3, 214-pound junior who showed both power and speed, piled up 125 yards on his first six carries, including scoring runs of 37 and 27 yards. He carried 23 times in all in topping his previous best of 149 yards last year.

Kollmorgen, who was thrust into the starting job as a freshman last year, completed 14 of his first 15 passes and finished 21 of 28 for 218 yards, no interceptions and the two touchdowns to Johnson, whose four TDs tied the school's single-game record.

Tormenting Iowa State with passes on short underneath routes, Kollmorgen was so effective in the early going that the Cyclones did not break up a pass until freshman linebacker Luke Knott knocked one away with 1:32 left in the first half.

Iowa State's Sam Richardson, making his third career start, completed 22 of 32 passes for 242 yards and two TDs and added 74 yards rushing on 21 attempts.

But the defensive failures and inconsistency in the new pistol offense doomed the Cyclones in a game that drew a crowd of 56,800, which matched the largest ever at Jack Trice Stadium.

The temperature at kickoff was 92 degrees, making it the warmest game on record at the stadium. Temperatures cooled to the upper 70s by the second half, though the humidity remained high.

Northern Iowa scored on its first three possessions, on drives of 69, 78 and 82 yards, as Johnson and Kollmorgen shredded a young Iowa State defense left even more inexperienced by the absence of senior cornerback Jansen Watson, who watched from the sideline in sweat clothes.

Johnson broke three tackles on a 37-yard touchdown run that put the Panthers up 7-0 and walked into the end zone on a 9-yard reception from Kollmorgen that made it 14-7.

On the Panthers' next possession, Kollmorgen completed four straight passes before runs of 13 and 27 yards gave Johnson his third TD and a 21-7 lead with 6:52 left in the half.

Richardson threw first-half touchdown passes of 59 yards to senior Justin Coleman -- his first career catch -- and 7 yards to James White. But the Cyclones stalled twice inside the Northern Iowa 20-yard line in the third quarter and had to settle for the Netten field goals.

The second opportunity came after Deon Broomfield forced and recovered a UNI fumble at the Panthers' 20. Sam Tim's sack of Richardson, one of five by the Panthers, and an incomplete pass forced the field goal.